1. Field of the Invention
This invention relates to a flapper check valve having a valve backer plate with a plurality of arcuate backer through holes, a valve port plate with a plurality of arcuate port through holes, and a flapper ring freely moveable between the plates for opening and closing communication between the backer through holes and the port through holes.
2. Description of the Prior Art
Existing flapper valves normally include a valve or port plate, a backer plate, an appropriate spacer, and flappers made of lightweight, flexible, abrasionresistant material such as fiberglass coated with TEFLON.TM. or another similar substance. Port plates normally have a plurality of circular through holes radially arranged such that a flapper ring can cover a radial row of the holes.
Each flapper ring is normally maintained in a predetermined position by pins which are inserted into the port plate. The ring flappers have little inertia and thus are easily displaced between the port plate and the backer plate.
Existing flapper valves use a center spacer to fix a predetermined gap between the valve plate and the backer plate. Fluid/gas flow capacity through the valve is a function of the gap or distance between the plates, the cross-sectional area and peripheral shape of the port openings or holes, and the pressure differential of the oscillating gas stream.
Existing flapper valves use valve plates and backer plates each having a multiplicity of holes with each hole having a relatively small diameter. Such relatively small diameter holes must be drilled or machined to achieve the proper number of holes in the relatively thick plates. Upon combustion and thus increased pressure within a combustion chamber, the back pressure forces the flapper rings against the holes in the valve plate and thus prevents back flow through the valve plate.
Increased flow through a valve can be achieved by increasing the number of through holes in the plate or by increasing the size of the holes in the plate. Thus to achieve certain flowrates, the valve plate and backer plate must have a relatively large diameter in order to accommodate the required multiplicity of circular holes. For example, an 8-5/8" diameter valve port plate according to existing designs may have 4 radially spaced circular arrays of circular holes. Such arrangement results in approximately 160 or more circular holes having approximately a 1/4" diameter. Obviously, fabricating such plates requires expensive drilling and/or other manufacturing methods. Such existing plates cannot be produced by stamping with a die tool because the plate is too thick and the circular holes are positioned too close together.
U.S. Pat. No. 4,752,209 discloses a pulse combustion burner feed valve for supplying air or fuel gas to a pulse combustion burner in response to oscillating burner pressures. The '209 patent teaches a backer plate having two circular arrays of backer plate openings which correspond in size and position with two circular arrays of circular valve openings in a valve plate. A central spacer is used to adjustably fix the distance between the plates. Upon assembly of the plates, the flappers are radially aligned with locator pins. The '209 patent teaches valve and backer plates constructed of 1/4" thick steel plate.
U.S. Pat. No. 4,687,435 discloses a pulse combustor having a valve mechanism for controlling air supply to a chamber. A smooth, ring-shaped elastic member is fitted on the outer periphery of a spacer and protects contact portions from wear. A plurality of valve guards are arranged on a combustion chamber side of a base plate. Each valve guard is fixed through a spacer to the base plate by a supporting screw.
U.S. Pat. No. 4,640,674 teaches a pulse combustion apparatus having a valve retainer which is used below each of a series of openings in a valve plate. The valve retainer has a disc-shaped portion and a boss that projects outwardly to one side of the disc-shaped portion. The boss is secured to the valve plate with a rivet that extends through a central opening in the boss and through an opening at the center of a circular series of openings in the valve plate.
U.S. Pat. No. 4,715,807 discloses a pulse combustion device having an air inlet valve assembly. The air inlet valve assembly includes an annular valve plate formed with a plurality of circumferentially and equally spaced air ports. A plurality of circumferentially and equally spaced air inlet valve units are mounted on the valve plate, on a common circular path concentric with a gas passage. Each air inlet valve unit includes a circular backer plate having circular holes. A circular air flapper is moveable between the valve plate and the backer plate and is lifted off the air port when applied with negative pressure from the mixing chamber.
U.S. Pat. No. 4,570,610 teaches a pulse combustion burner for a cooking surface. The pulse combustion burner has a flapper air valve comprising an end wall secured to a housing, a flapper membrane and a backer plate. The '610 patent also discloses the valve connected to a mixer chamber through a pipe coupling seal welded to a mixer head at a port extending through the sidewall of the mixing head.
U.S. Pat. No. 4,336,791 teaches a pulse combustion apparatus having inner and outer perforated discs which are essentially identical and are provided with respective sets of circular openings. The inner and outer discs have a relatively large circular central opening surrounded by an annular series of relatively small openings. Each relatively small opening is surrounded by a series of intermediate sized openings.